Most emulators have just been built/developed with what people are used to, or what they like, which has become more similar over the years. Your questions confuses me a bit, but if you are actually looking for a good front-end for your standalone emulators, try emudeck: https://www.emudeck.com/

AdNauseam is based on uBlock and does some extra stuff as well, in case anybody was curious. Link

The cheap fix would be to get the color-matching stretchable filler, but those are more used for holes; I think it might introduce more problems when the floor shifts.